SOLUTION: a cyclist circles for x hours for 12km per hour and y hours for 18km per hour,altogether he circles 5 hours for 78km per hour.what is x and y

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Question 702440:
a cyclist circles for x hours for 12km per hour and y hours for 18km per hour,altogether he circles 5 hours for 78km per hour.what is x and y
Answer by checkley79(3341) About Me  (Show Source):
You can put this solution on YOUR website!
D=RT
78=12T+18(5-T)
78=12T+90-18T
78-90=-6T
-12=-6T
T=-12/-6
T=2 HOURS FOR THE 12 MPH. TRIP.
5-2=3 HOURS FOR THE 18MPH TRIP.
PROOF:
78=12*2+18*3
78=24+54
78=78